Lubricant composition



Patented Oct. 22, 1946 LUBRICANT COMPOSITION Carl Winning, Westfleld,and John G. McNab,

Cranford, N. J., assignors to Standard Oil Development Company, acorporation of Delaware No Drawing. Application May 28, 1941, SerialNo.-395,614

Claims.

The present invention relates to improvements in lubricants andespecially to the improvement of lubricating oils principally useful forinternal combustion engines operating under severe conditions. Theinvention will be fully understood from the following description.

Lubricating oils which exhibit improved performance under all types ofoperating conditions when used for the lubrication of heavy dutygasoline engines and for Diesel engines are coming into greater andgreater demand. It has been proposed to add various ingredients to theseoils to improve their behavior in such service. In accordance with thepresent invention, certain ingredients are added to bring about greaterengine cleanliness and to avoid ring sticking, varnish formation andcarbon deposition, also to avoid corrosion of metal parts. It istherefore an object of the present invention to provide addition agentsfor lubricating oils of the type described which not only exhibit suchdetergent and corrosion inhibiting properties, but which will notincrease the pour point of the oil and will blend readily with the oilto form a solution which will remain homogeneous both during storage andduring use.

It is known that various salts, particularly metal salts, have abeneficial effect on lubricating oils to which they are added, that is,these salts exhibit detergent properties by inhibiting the formation ofsludge deposits and in promoting general cleanliness in the engine; andthey have the further very valuable property of preventing the normaldeterioration of oils which results in the corrosion of metal parts,particularly the cadmium-silver and copper-lead alloys which are nowwidely used in bearings. Many metallic salts have been proposed for usein lubricants, and among the most valuable of these are the metallicsalts of inorganic acids having substituent oil-solubilizing organicgroups. For example, the alkaline earth salts of substitutedorthophosphoric acids, such as calcium cetyl phosphate, calcium (cetylphenyl) phosphate, aluminum octadecyl phosphate and chromium oleylphosphate, and the cadmium, tin and cobalt mahogany sulfonates are amongthose which have been disclosed as addition agents.

It has been found, however, that there is one drawback to the use ofsuch salts. and that is their tendency to promote the deposition ofvarnish on the engine parts with which the oil containing the salt comesin contact. Such varnish formation is very Objectionable, since itcontributes to ring sticking, and when the deposits become sufiicientlyheavy on piston skirts the pistons may freeze. to the cylinder walls. Ithas been found, in accordance with the present invention, that thistendency to form varnish can be materially reduced and often entirelyeliminated if a small amount of a high molecular weight alcohol is addedto the oil containing the metallic salt. The action of the alcohol isnot understood, since the addition of alcohol alone to uncompounded oilssometimes actually increases the amount of varnish formed. It isevident, therefore, that the alcohol and salt cooperate with each otherin some way to mutually inhibit the normal tendency of each to produce acertain amount of varnish.

The invention may be defined in its broadest terms as the use in minerallubricating oils of a higher alcohol together with a salt of aninorganic acid which contains at least one oil-solubilizing substituentorganic group.

The higher alcohols suitable for; use in conjunction with the metalsalts arepieferably those having 8 carbon atoms or more, though ingeneral alcohols falling in the C12 to C20 range are preferred. Thesealcohols include the saturated, straight or branched chain aliphaticalcohols, such as octyl alcohol, lauryl alcohol, cetyl alcohol, stearylalcohol and the like; the corresponding olefinic alcohols, such as Oleylalcohol; cyclic alcohols, such as naphthenic alcohols; and arylsubstituted alkyl alcohols, for example, phenyl octyl alcohol, oroctadecyl benzyl alcohol; or mixtures of these alcohols, which may bepure or substantially pure synthetic alcohols. There may also be usedmixed naturally occurring alcohols, such as those found in wool fat(which is known to contain a substantial percentage of alcohols havingabout 16 to 18 carbon atoms) and in sperm oil (which contains a highpercentage of cetyl alcohol); and although it is preferable to isolatethe alcohols from these materials, for some purposes the wool fat, spermoil or other natural products rich in alcohols may be used as such.Products prepared synthetically by chemical processes may also be used,such as a1- cohols prepared by the oxidation of petroleum hydrocarbons,e. g., paraffin wax, petrolatum, etc. In general, the effectiveness ofthe alcohol increases with its molecular weight and straight chainalcohols have been preferred in view of their greater availability.

The amount of higher alcohols to be used may vary between theapproximate limits of 0.01 to 5.0%, though generally from 0.1 to 1.0% ispreferred, the exact amount to be used depending upon the severity ofthe operating conditions and upon the type of lubricating oil base stockused.

The salts used in the lubricating compositions of the present inventionmay, in general, be any metallic salts of inorganic acids containing atleast one organic group which serves to render the salt soluble inmineral oil. This organic group may appear as a substituent for one ofthe hydrogen atoms of the inorganic acid from which the salt wasderived, or the group may even appear as a substituent'for a hydroxylgroup of such acid, as in the case of salts of organic sulfonic acidswhich may be considered as sulfuric acid in which one hydroxyl group issubstituted by an organic group. Since there must be at least one metalatom or equivalent radical and at least one solubilizing organic groupin the salt, such salt must necessarily be derived from a polybasicinorganic acid.

The organo substituted inorganic acids of which the preferred salts ofthe present invention may be considered as derivatives may be any organomay be any metals, and the salts may include salts of amines, pyridineand similar basic nitrogen compounds, ammonium (NH4) or salts ofammonium containing one to four substituent organic radicals, such asthe quaternary ammonium salts, and the corresponding salts ofphosphonium, sulfonium, arsonium, and stibonium bases. Especiallypreferred are the metals of groups I, II, III and VIII of the periodictable. Salts of group II, such as magnesium, calcium and barium salts,have been found to be particularly effective.

The oil-solubillzing substituent organic group which appears as part ofthe salt structure may be of any type, providing only that it impartsappreciable oil solubility to the salt. Thus, the substituent groups maybe alkyl, alkoxy, aryl, aralkyl or heterocyclic groups, and such groupsmay, furthermore, contain substituent groups and atoms, for example,amino, nitro, hydroxy or mercaptan groups, or halogen atoms.

Typical of the metallic salt compounds preferred for use in accordancewith the present invention are the following, which are illustrated bystructural formulas showing the structures which a few of the mostpreferred compounds I are believed to possess, R in the formulasdesigsubstituted inorganic acids capable of forming oil soluble metallicsalts, such, for example, as ootadecyl phosphoric acid (CisHs70(OH)2PO),dodecyl phosphoric acid (C12H25O( OH)2PO), diisobutylphenyl phosphorousacid amyl benzyl sulfurous acid (C5H11C6H4CH20) (OH) SO] and dioctylsulfamic acid [CsH17)2N(OH) S02], as well as comparable substitutedarsenic, arsenious, arsinic, arsonic, stannic, stannous, chromic,chromous, plumbic, aluminic and silicic acids and the like, also thecorresponding acids in which sulfur, selenium 0r tellurium issubstituted for oxygen. Included also are the derivatives of the abovenamed acids in which halogen, oxygen, nitrogen and sulfur substituentsappear in the organic group. Especially preferred salts are thephosphates and thiophosphates, also sulfates and sulfonates,particularly those derived from petroleum.

In the foregoing discussion, as well as elsewhere in this specification,the diisobutyl radical forming part of various compounds is to beunderstood as being derived from diisobutylene, and such radical mayalso be designated as tetramethyl butyl.

The metals which may appear in the salts which are added to the minerallubricating oils Among the most preferred substituted inorganic salts,to be added to lubricating oils in conjunction with the higher alcoholsdescribed above, are the following, which are given by way ofillustration only: calcium cetyl phosphate, barium dioctyldithiophosphate, diisobutyl di(triamylammonium phenolate) sulfide andmagnesium petroleum sulfonate.

The substituted inorganic salts described above may be prepared invarious ways. One typical method, such as that described in U. S. PatentNo. 2,228,659, consists in reacting an appropriate inorganic oxide orsulfide, for example, an oxide or sulfide of phosphorus, with analiphatic alcohol to form an alkyl substituted inorganic acid, which issubsequently reacted with an alkali to form the alkali salt, and thedesired metal salt is formed by precipitating from a solution of thealkali salt on adding the appropriate metal ion. In the case of thepreparation of salts of sulfonic acids, such as the calcium or bariumsalts, alkali salts of sulfonlc acids, well-known as emulsifying agentsand obtained from petroleum fractions or other hydrocarbon materials bymeans well known to the art, may be reacted in appropriate solutionswith calcium or barium salts to form the corresponding calcium or bariumsoaps of the sulfonic acid.

Generally, the amount or the salt to be used in the compositions of thepresent invention should be between the approximate limits of 0.02 and2.0%, and preferably from 0.1 to 1.0%, the exact amount to be useddepending to a certain extent on the particular compound, the amount ofhigher alcohol used, the character or the mineral oil base and theoperating conditions oi the engine in which the lubricant is to be used.

The lubricating oil base stock for this invention, in its broadestaspect, may be any mineral oil distillate or blend and may contain aresidual oil, or it may be a fraction resulting from various physicaland chemical refining treatments, such as solvent extraction,precipitation, etc. For the best result, however, the base stock chosenshould usually be that oil which, without the additives present, givesthe optimum performance in the service contemplated. For the lubricationof medium and high speed Diesel engines it is general practice to use alubricating oil base stock prepared from naphthenic or aromatic crudesand having a Saybolt viscosity at 210 F. of 45 to 90 seconds and aviscosity index of to 50. However, preference is often expressed for oilof very high viscosity index (100 or higher) and such oils are to beconsidered as within the scope of the present invention. The oils may befree from other addition agents or they may contain other materials forparticular purposes, for example, thickeners, sludge dispersing agents,dyes, pour depressants, viscosity index improvers, solvents, oilinessagents and antioxidan In the following examples there are described indetail methods of preparing a number of the preferred addition agents ofthe present invention and tests showing their use in a typical Dieseloil, together with the results obtained in the test of the amount ofvarnish film formation resulting from the use of the prepared blends.These examples are to be considered as illustrative only and not aslimiting the scope or the invention in any way.

Example I For the preparation of calcium octyl thiophosphate, a mixtureof 444 grams of phosphorus pentasulfide, 1170 grams of octylalcohol, and250 grams of. sodium carbonate was heated gradually to 70 C. and finallyto 110 C. with agitation until. evolution of carbon dioxide and hydrogensulfide had ceased. The reaction mixture was filtered and then dilutedwith 500 cc. of absolute ethyl alcohol. A solution of 2 mols of calciumnitrate in 1 liter of ethyl alcohol was added and the mixture filteredto remove the sodium nitrate formed. The ethyl alcohol was removed fromthe filtrate under vacuum and the residue diluted with 1.5 liters ofpetroleum ether and again filtered to remove the unreacted calciumnitrate. The latter filtrate was contacted with metallic mercury toremove active sulfur as mercuric sulfide and again filtered. Thepetroleum ether was stripped from the product and Example II For thepreparation of barium octyl thiophosphate, 520 grams of octyl alcohol(2-ethylhexanol) and 222 grams of powdered phosphorus pentasulfide wereplaced in a reaction flask and heated to C. with agitation. Evolution ofhydrogen sulfide began at about 50 C. and the reaction was practicallycomplete after 3-4 hours at 80 0., but the mixture was agitated at 40-50C. overnight with a slow stream of air passing through the flask.Titration of the crude product showed that 90.2% of the theoreticalamount of octyl thiophosphoric acid,

. s (CIHX'IO)IP SH had formed. The crude product was filtered to removeunreacted phosphorus pentasulflde. and

392 grams of the filtrate (containing 1 mol or 354 grams of octylthiophosphoric acid) were neutralized with alcoholic sodium hydroxide.After removing the alcohol undervacuum, 422 grams of a clear, strawcolored, rather viscous oil were obtained. 75 grams of the sodium octylthiophosphate thus formed were dissolved in 150 cc. of absolute alcohoL.A mixture of cc. of the alcohol and 36 grams of barium bromide was addedwith stirring. The alcohol was removed by evaporation and the residuedissolved in ether and filtered. Upon removal of the ether from thefiltrate 63 grams of a straw colored, semisolid material (barium octyldithiophosphate) were obtained.

Example III For the preparation of a barium soap of petroleum sulfonicacids a commercially available 'alcoholic solution of sodium salts ofmahogany sulfonic acids was employed, containing 12.75% of salts, 2.25%of mineral oil and 57.9% of isopropyl alcohol, the remainder beingwater. To

400 grams of this solution was added an aqueous Example IV Mineral oilblends were prepared by adding in each case 1% of calcium octylthiophosphatc,

barium octyl thiophosphate or barium soap of petroleum sulfonic acids,prepared as described above, to a base lubricating oil consisting of adistilled Coastal oil of 55 Saybolt seconds viscosity at 210 F., also byadding 0.5% of stearyl alcohol to portions of each of these blends andto a blank oil sample. These oil blends, as well as a blank oil sample,were submitted to the Indiana oxidation test (Ind. Eng. Chem, Anal. Ed.,v. 6, p. 419 (Nov. 15, 1934)), modified as described below so thatvarnish film formation could be measured. In each oil sample tube aglass plate approximately 3 inches by 1 inch was placed. At the end of24 hours, using the conventional Indiana oxidation test procedure, theplate was removed, washed with naphtha, air dried and weighed. From theknown weight of the glass plate at the beginning of the test the weightof varnish formed was calculated. The results of the tests are given inthe following table:

Varnish formed in Oil or oil blend 24 hrs., mg.

The above test ls intended to indicate the extent to which variouslubricating oils will tend to cause the deposition of varnish-likematerials on piston skirts and other engine parts. As mentioned earlierin the specification, such varnish formation is undesirable.

It will be seen from the above data that in each instance when thealcohol was added to the blend of mineral oil and metal additive,varnish formation was reduced considerably and in most cases the amountwas less than that obtained with either the alcohol or the metalderivative alone.

The present invention is not to be considered as limited by any of theexamples described herein, which are given by way of illustration only,but it is to be limited solely by the terms the appended claims.

We claim:

1. A machinery lubricant suitable for use at high temperaturescomprising a major proportion of a mineral oil base stock, a minorproportion, sufllcient to impart substantial detergent properties tosaid lubricant, of a metal salt of a polybasic inorganic acid whichcontains at least one oil-solubilizing organic group, and a minorproportion, sufllcient to inhibit varnish formation, of a higheralcohol.

2. A lubricant according to claim 1 in which the metal of the metal saltis selected from the class consisting of the metals 01 groups I, II,III, and VIII of the periodic table.

3. A lubricant according to claim 1 in which the metal of the metal saltis a 'metal of group II of the periodic table and in which the alcoholcontains at least 8 carbon atoms per molecule.

4. A lubricant according to claim 1 in which the metal salt is a salt ofan alkylated acid of phosphorus and in which the alcohol contains atleast 8 carbon atoms.

5. A lubricant according to claim 1 in which the metal salt is a bariumsalt of petroleum sulionic acid and in which the alcohol contains from12 to 20 carbon atoms per molecule.

6. A machinery lubricant suitable for use at high temperaturescomprising a major proportion of a mineral oil base stock, about 0.02%to about 2% of a salt of a metal of group II of the periodic table and apolybasic inorganic acid containing at least one oll-solubilizingsubstituent alkyl group, and about 0.01% to about 5% of an alcoholhaving at least 8 carbon atoms per molecule.

7. A lubricant according to claim 6 in which the salt is an alkalineearth metal salt of an octyl thiophosphoric acid and in which thealcohol is stearyl alcohol.

8. A lubricant according to claim 6 in which the salt is a-barium soapof petroluem sulionic acid and in which the alcohol is stearyl alcohol.

9. A machinery lubricant suitable for use at high temperaturescomprising a major proportion of a mineral oil base stock, about 1% ofan alkaline earth metal salt of an octyl thiophosphoric acid and about0.5% of stearyl alcohol.

10. A machinery lubricant suitable for use at high temperaturescomprising a major proportion of a mineral oil base stock, about 1% of abarium soap of petroleum sulfonic acid and about 0.5% of stearylalcohol.

CARL WINNING. JOHN G. McNAB.

